“This ‘famine reaction’, a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available.”

Dieting difficulty

Prof Byrne said researchers in the past had shown as dieting continued weight loss became more difficult.

Prof Byrne said this two-week intermittent diet proved to be a more successful means of weight loss compared with continuous dieting.

But other popular diets which included cycles of several days of fasting and feasting were not any more effective than continuous dieting.

These include the fashionable 5:2 diet which severely restricts calorie-intake for two days of the week.

She said: “There is a growing body of research which has shown diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting.

Critical break

“It seems that the ‘breaks’ from dieting we have used in this study may be critical to the success of this approach.

“While further investigations are needed around this intermittent dieting approach, findings from this study provide preliminary support for the model as a superior alternative to continuous dieting for weight loss.”

About two-thirds of all dieters pile their weight back on within three years of hitting their dream targets.

Harriet Jenkins was named Slimming World’s Woman of the Year after she lost 15st in as many months.

In fact 40 per cent of those who lose more than 7st put on at least that much again.

It is called the Fat Trap.

Prof Byrne said: “We’re interested to understand the biology a bit further to maybe refine the approach and get greater results into the future.”